Micron and sub-micron feature replication of amorphous polymers at elevated mold temperature without externally applied pressure

Abstract

The focus of this study is on the ability of amorphous polymers to replicate micron and sub-micron features when molded at an elevated mold temperature without externally applied pressure. Molding was performed using three different types of amorphous polymers: cyclo-olefin copolymer (COC), polystyrene (PS) and poly (methyl methacrylate) (PMMA) on a silicon mold containing surface features as small as 700 nm in depth and aspect ratios ranging from 5 to 0.02. In this study, processing temperatures were selected in order to match the viscosity for all polymers used. Polymer viscosity was characterized via cone and plate rheometry and wettability was characterized via contact angle analysis to quantify interfacial effects. Feature replication was assessed using scanning electron microscopy (SEM) and atomic force microscopy (AFM) to compare the molded feature depth ratio. It was observed that for the features with an aspect ratio (depth/width) bigger than 2 the depth ratio of the molded parts decreases. PS shows the best replication because of high wettability behavior. PMMA shows the intermediate replication because of dipole-dipole interaction and its lower diffusion coefficient than PS. COC has the worse replication especially in low aspect ratio because of sticking to the silicon oxide layer. PS has the best surface roughness among all polymers.

Multi-scale filling simulation of micro-injection molding process

“…Here, I is the identity matrix, n is interface normal, σ equals the surface tension coeffient ) / ( m N and δ equals a Dirac delta function that is nonzero only at the fluid interface [20].…”

On The Role of Wetting, Structure Width, and Flow Characteristics in Polymer Replication on Micro‐ and Nanoscale

“…But as soon as the melt freezes at the mold wall, wetting effects can probably be neglected. Mosaddegh and Angstadt proved the influence of interfacial wetting showing differences in the filling behavior of silicon submicron structures without external pressure of three amorphous polymers. The temperatures were adapted in such a way that the viscosity at a shear rate of zero ( η 0 ) of all polymers were on the same level.…”

Study on the replication quality of micro-structures in the injection molding process with dynamical tool tempering systems

“…Therefore, some authors have already presented their experimental results in the replication of different surface structures (Huang 2007;Giboz et al 2007;Yao and Kim 2002;Mosaddegh and Angstadt 2008;Pranov et al 2006;Xu et al 2005;Mönkkönen et al 2002). Some of them have also carried out numerical results with micro scale factors like wall slip and mold surface roughness, and compared their results to experimental tests.…”